1. Field of the Invention
The present invention relates to an apparatus for identifying and selecting conductors in a multi-conductor cable or conduit, the ends of which are located remote from each other. The invention more particularly relates to such an apparatus which further provides for voice communication between workers located at each end.
2. Description of the Prior Art
The sorting and testing of electrical wires within multi-conductor cables or conduits is a time-consuming and tedious process contributing greatly to the installation cost and time. The task is particularly difficult when the cable or conduit ends are located remote from each other, so that workmen on each end are not in visual or audible contact. The provision of voice communication between workers at each end of the cable or conduit significantly simplifies the task. When sorting and testing conductors during the construction of large buildings, it is particularly difficult to provide voice communication between workers on different floors, since the metal building structure interferes with radio communications.
The above-mentioned difficulty is experienced in many different fields, such as the installation of electrical wiring and the installation and maintenance of video and/or telephone cables.
A typical method of identifying conductors in cables or conduits requires the services of at least two workmen, one at each end. One workman selects a suitable pair of conductors and imposes a tone across said pair, while the other workman at the other end of the cable uses a probe, amplifier and suitable receiver in an attempt to identify the tone as he probes the various conductors within the cable. After a conductor pair is identified, suitable equipment may then be used to establish voice communication between the workmen. The selecting process then continues with a tone being applied to another pair by one workman, while the other again probes to identify the second pair. During initial installation any electrical signal can be used; however, for subsequent testing, signals must be used that do not interfere with the normal use of the conductors.
The above-mentioned difficulty was described in an article, "Improved Pair Identification Cuts Cable Handling Costs", printed in Telephony, dated Aug. 9, 1971, at pp. 68-72. The article points out the need for various types of tone generators to generate a `silent tone` which cannot be heard by the telephone subscribers and which would not interfere with special telephone circuits. The article recommends that an extra talk pair be provided for communication between the two men performing the identification and selection.
A more sophisticated pair identifying apparatus is disclosed in U.S. Pat. No. 2,799,739, which provides for the identification of cable pairs in a telecommunications system, wherein only one splicer is required at a location remote from a central office.
The prior art apparatus are either inconvenient to use or are complex and expensive and not particularly adaptable to the rugged handling associated with initial installations at construction sites. There clearly was a need for a convenient, inexpensive and rugged continuity tester that included voice communication capability, a pair reversal indication, and a conductor short indication.